Start performance trace

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

It discloses that only one trace can run at a time, the default recording duration (~5s), the output format (raw trace JSON), and the distinction between returning just an event count vs. saving the full trace. This adds significant behavioral context beyond the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is concise, well-structured, and front-loaded with the core purpose. Each sentence provides essential information—categories, defaults, constraints, and output handling—without any redundant or filler content.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description fully covers the tool's behavior given its optional parameters and existing output schema. It addresses the main use cases (self-contained trace vs. manual stop), a key constraint (one trace at a time), and how to handle results, making it complete for a tool of this complexity.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so the baseline is 3. The description adds value by explaining the practical impact of file_path (keeping data vs. just an event count) and clarifying the default behavior of reload and auto_stop, going beyond the schema's field descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool records a Chrome performance trace of page load or interaction, and it explicitly lists the captured categories. This differentiates it from sibling tools like performance_stop_trace and other page-related actions.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description explains the default behavior (reload + auto_stop), when to set auto_stop=false and use performance_stop_trace, and the consequence of omitting file_path. This gives clear when-to-use guidance and references an alternative tool.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.